Santa Ana winds: Pasadena is reporting hundreds of trees down and one wind-related injury. Hundreds of thousands of Southern California residents are without power from the worst Santa Anna winds in more than a decade.

Pasadena, Calif., saw winds that blew over trees like this one on the corner of North San Gabriel Avenue and East Colorado Boulevard, Thursday. Some of the worst winds in years blasted through California overnight, sweeping through canyons, gusting up to 97 mph, and toppling trees and trucks while knocking out power to hundreds of thousands of people.

Los Angeles — Southern California is being buffeted by the worst windstorm in more than a decade – gusts have been clocked as high as 100 miles per hour – resulting in widespread power outages, diverted flights, hundreds of trees down, and the city of Pasadena on an emergency footing.

The high Santa Ana winds, which began late Wednesday, have rattled residents and businesses all over the West, from Utah to Southern California. Hundreds of thousands of people are without power, and colleges, schools and at least one movie studio have shut down.

While some meteorologists are referring to the storm as an especially severe form of the Santa Ana winds that Southern California experiences at this time of year, others say the storm’s wind patterns are unusual, affecting communities that don’t usually experience such violent weather.

According to the National Weather Service, what’s driving the strong winds is a large, cold, low-pressure system centered over Needles, California. The service expects the system to stay put, rotating counter-clockwise for at least another day, although with declining power.

“These are the worst winds we have seen in at least a decade,” says Stuart Seto, a National Weather Service specialist in Oxnard, near Los Angeles. He says he expects the winds to continue gusting into the weekend, with winds as high as 55 mph through Saturday. “If you are on a motorcycle or a high profile vehicle, you may want to stay off the Interstate,” he adds, “as the cross winds will continue to be very strong.”

Santa Ana or not, the winds are unusual in the areas they are hitting, says Ken Clark, a Southern California meteorologist for Accu Weather, the largest private weather forecasting service.

Typically, the traditional Santa Ana winds would have swept through the Ventura County region in the Los Angeles area, Mr. Clark says.

But the wind pattern from this storm has taken an unusual course, hitting areas that are not accustomed to the Santa Anas. “That’s when you start to see more damage,” he says, because trees in particular are not accustomed to taking such a beating.

Pasadena was one of the worst hit areas, with some 450 city-owned trees downed by Thursday afternoon and at least one wind-related injury resulting in hospitalization.

“The town is rattled,” says city spokesman, Tim McGillivray. At least 16 city agencies have been put on high alert, with a citywide emergency footing imposed to handle downed power lines and other emergency calls.

“We don’t know how many trees have been weakened by the winds,” he says, “but at the moment, all our personnel are working to help clear debris and answer emergency calls.”

According to the California Department of Public Works, there is extensive damage throughout Southern California, including power outages and blowing debris.

Power was out at Los Angeles International Airport for at least an hour, diverting flights to nearby airports. An estimated 300,000 Southern California residents were without power on Thursday.

The National Weather Service has put out high wind warnings and advisories for parts of California, Utah, Nevada, Wyoming, Arizona and New Mexico. The weather system is expected to eventually bring some nasty weather to Oklahoma, Missouri and Indiana.

As of 3 p.m. Thursday, the Los Angeles Department of Water and Power said it had restored power to 80,000 electrical customers since the windstorm started Wednesday night, but that nearly 1 in 10 of its customers were without power (130,000 out of 1.4 million), with several neighborhoods experiencing outages as a result of the high winds.

It said it had called in repair crews from elsewhere in California and out of state to get power back, but that customers still without power could expect delays of up to 48 hours.